1. Field of the Invention
The present invention relates to an image forming apparatus such as a printer, and more particularly, to a print head of an inkjet printer.
2. Description of the Related Art
An inkjet printer comprises a plurality of nozzles in a print head and a plurality of piezoelectric elements which correspond to the nozzles one by one. Here, a piezoelectric element means a device that generates electricity when a pressure is applied to and changes in shape when a voltage is supplied generating a pressure. When print data to be printed are input to the inkjet printer, a voltage is supplied to each piezoelectric element in the printer head according to the print data. As a part of the piezoelectric element to which a voltage is supplied protrudes to eject droplets of ink contained in the print head through the corresponding nozzle.
A normal operation of the print head is obviously needed to print data to be distinct. For example, if ink is not normally ejected due to the clogging of nozzles, it is impossible to print data to be distinct. In order to check whether the print head normally operates, for example, when intending to eject ink through all nozzles, it is visually inspected whether ink is smoothly ejected from each of the nozzles with a lens or a monitor or by checking a printed sheet, which is printed for testing. However, both of these checking methods are considerably time consuming. For this reason, inkjet printers do not check during their printing operation whether the print head normally operates or not, for speedy printing. As a result, even when nozzle failure occurs during the printing operation, this failure is ignored and ink is wasted for the defective printed sheet.